1. Field of thc Invention
This invention relates to an ink discharge recording device in an ink jet recording apparatus, and in particular to an ink discharge recovery device provided with cleaning means for cleaning the discharge port surface of a recording head.
2. Related Background Art
With an ink jet recording apparatus, it has sometimes been the case that in addition to the entry of air into a recording head and the adherence of paper powder and dust or viscosity-increased ink to the surroundings of the orifice of that as in the recording head (the vicinity of an opening for discharging ink therethrough), unsatisfactory discharge such as non-discharge of the ink or the deviation of the direction of discharge is caused by the collection of ink around the orifice.
So, solutions such as the provision of means for removing the foreign materials which cause the unsatisfactory discharge have been adopted.
In an ink jet recording apparatus, as means for preventing the ink discharge ports from clogging due to the increase in viscosity of ink caused by evaporation of the ink solvent, the adherence of dust or the creation of bubbles, there is a construction as described, for example, in U.S. Pat. No. 4,045,802 and U.S. Pat. No. 4,603,931, wherein the ink discharge port surface of the recording head is covered with a cap to thereby shield the ink discharge port surface from the atmosphere and keep the discharge ports in a good condition, and a construction in which a discharge recovery device for causing ink to be discharged by a suction pump or the like is provided.
Such a capping operation and such a discharge recovery operation are usually effected when a carriage is at its home position.
Also, for removing ink and dust present near the discharge port, there is a construction as described in U.S. Pat. No. 4,112,435, U.S. Pat. No. 4,364,065 and Japanese Laid-Open Pat. Application No. 58-94472 wherein as cleaning means, a flexible blade formed of rubber or like material is used to wipe the front face of the recording head (the surroundings of the discharge ports) (this will hereinafter be referred to as prior art .circle.1 ). As the cleaning means, besides the above-mentioned one, there is a construction as described, for example, in U.S. Pat. No. 4,306,245 wherein a brush and an ink absorbing member slide across around the discharge ports (this will hereinafter be referred to as prior art .circle.2 . Further, there is a construction as described in Japanese Laid-Open Pat. Application No. 59-83664 wherein the surroundings of the discharge ports are first wetted by sponge impregnated with water and then are wiped by a blade (this will hereinafter be referred to as prior art .circle.3 ).
However, it has been found from numerous experiments that in the above-described prior art, .circle.111 - .circle.3 , recovery from unsatisfactory ink discharge is not fully accomplished in some cases and there is the necessity of improvement.
In the case of prior art .circle.1 , liquid drops of relatively low viscosity such as ink drops adhering to the surroundings of the discharge ports and dewdrops formed on the surroundings of the discharge ports by the rise of the humidity in the apparatus can be removed by the discharge recovery operation using suction or the like. However, when an attempt is made to resume recording after recording has been ceased or stopped for a long time, the occurrence of non-discharge is eliminated by the discharge recovery device, but the direction of flight of ink deviates and thus, it has become impossible to cause ink droplets to adhere to a accurate positions on the surface of a recording medium and images formed thereon have sometimes been disturbed.
In the case of prior art .circle.2 , cleaning is repetitively effected at the home position and therefore, the stain or fluffing of the surface of the absorbing member attributable to the durability of the absorbing member causes foreign materials to adhere to the surroundings of the discharge ports, and this has sometimes resulted in unsatisfactory ink discharge.
In the case of prior art .circle.3 , the sponge retains water content therein and therefore, the rise of the humidity in the apparatus is expedited and the total amount of water drops adhering to the surroundings of the discharge ports due to dew formation is increased, and this has increased the wiping operation by the blade and thus, this could not be a radical improvement.
So, recording tests have been carried out under all conditions while observing the surroundings of the discharge ports of the recording head and the causes of unsatisfactory ink discharge have been thoroughly investigated.
As a result, it has been found that unsatisfactory discharge is attributable to the fact that the state of the ink adhering to the surroundings of the discharge ports OF changes as shown in FIGS. 1A -1D of the accompanying drawings. If, as shown in FIG. 1A and 1B, ink adheres as drops ID to the surroundings of the discharge ports OF, like dew, and is dried up, the ink assumes a state of very thin film ID' on the surroundings of the discharge ports OF as shown in FIGS. 1C and 1D.
Such an ink film 1D' has often been created when non-recording has lasted long. Heretofore, it has been known that unsatisfactory discharge occurs when recording is resumed after a long downtime of recording, but the cause thereof has been regarded as being attributable to an increase in the viscosity of ink or entry of air into ink. Certainly, most of the causes of non-discharge are the clogging resulting from an increase in the viscosity of ink and entry of air, but nobody has been aware that the cause of the deviation of the direction of ink discharge is attributable to the film of ink as noted above. Further, such a film has reduced the ink-repellent property of the discharge port surface and has induced a state in which ink is ready to such surface.
In view of the above-noted fact, it has been studied, through numerous repetitive experiments what is the construction of an ink jet recording apparatus in which the causes of unsatisfactory discharge can be eliminated most effectively and good recorded images can be obtained.
As a result, it has been found that as the cleaning means for the discharge port (orifice) surface of the ink jet recording apparatus, it is still preferable from the viewpoints of the effect of wiping and the problem of the durability of the cleaning means to remove ink drops, pools of ink and formed dew on the discharge port (orifice) portion by the aforementioned flexible blade. In an apparatus provided with a heating and fixating heater for expediting the fixation of ink, particularly, the ink adhering as a recorded image to the recording medium, the probability with which dew is formed by the evaporation of the water content of the ink becomes high and the role of the blade is very great. However, if ink drops or pools of ink adhere to the surroundings of the discharge ports for a long time and form very thin film or the like on the surroundings of the discharge ports, the direction of discharge is made unstable by the film even if pools of ink are apparently eliminated, and in addition, the ink-repellent property of the discharge port surface is reduced and pools of ink become ready to be created and thus, discharge misdirection becomes ready to occur. Such ink film could not be fully removed by the cleaning by the blade a previously described.